Icebergs are large chunks of ice that break off from glaciers. This process is called Calvin. Icebergs float in the ocean, but are made of frozen freshwater, not saltwater.
Most icebergs in the Northern Hemisphere break off from glaciers in Greenland. Sometimes they drift south with currents into the North Atlantic Ocean. Icebergs also calve from glaciers in Alaska. In the Southern Hemisphere, almost all icebergs calve from the continent of Antarctica.
Smaller ones such as Bergy bits are floating sea ice that stretch no more than 16.5 feet above the ocean. Growlers are even smaller.
Some icebergs near Antarctica can be as big as Sicily, the largest island in the Mediterranean Sea.
As little as one-eighth of an iceberg is visible above the water. Most of the mass of an iceberg lies below the surface of the water.
There are many different kinds of icebergs — Brash ice, for instance, is a collection of floating ice and icebergs no more than 6.5 feet across. A tabular berg is a flat-topped iceberg that usually forms as ice breaks directly off an ice sheet or ice shelf.
Icebergs that drift into warmer waters eventually melt.
Scientists estimate the lifespan of an iceberg, from first snowfall on a glacier to final melting in the ocean, to be as long as 3,000 years.